A typical large truck has a cab where a driver sits to operate the truck. When the driver wishes to start the engine, he operates an ignition switch, typically by inserting a key into a barrel of the switch and turning it clockwise from OFF position to CRANK position against an opposing force of an internal return spring. In the process, the switch passes through IGNITION position.
In CRANK position, the ignition switch energizes IGNITION and CRANK circuits in the truck's electrical system causing various engine systems to begin operating so that the engine is fueled and the starter motor cranked. Once the engine has begun to run under its own power, the driver can release the key to allow the internal return spring to return the switch from CRANK position to IGNITION position. IGNITION position may sometimes be referred to as ON position. The driver can then accelerate the engine by depressing an accelerator pedal.
When the driver desires to turn off the engine, he turns the ignition switch counterclockwise from ON position to OFF position. Turning the key farther counterclockwise beyond OFF position places the switch in ACCESSORY position, a position that energizes certain ACCESSORY circuits in the truck without the engine running. Those ACCESSORY circuits are also typically energized when the ignition switch is in IGNITION position, but not when the switch is in either OFF position or CRANK position.
When a truck is being serviced, it may be desirable to perform certain procedures that involve running the engine. Those procedures may require that the engine be cranked, and then accelerated and decelerated in various ways after the engine has begun running under its own power, and ultimately turned off. When those procedures are performed while the truck is parked, the transmission should obviously not be in a forward or reverse drive gear.
Some procedures may be more conveniently performed by service personnel from a location other than inside the cab. Depending on the particular type of the particular truck, it may not even be possible for personnel to enter and exit the cab during some procedures. For example, a cab-over truck may require that the cab be unlatched from the chassis and then swung upwardly on the chassis in order to obtain access to the engine which underlies the cab when the cab is latched to the chassis for normal driving.
Accordingly, an ability to operate the engine from a location outside the cab is desirable for servicing some motor vehicles, such as certain large trucks like cab-overs. Service personnel need to be able to mimic functions of the ignition switch and accelerator pedal from a remote location to crank, accelerate, decelerate, and stop the engine.
Having a duplicate ignition switch and accelerator control outside the cab however raises potential safety issues. Any remote control system for starting, operating, and stopping an engine in a motor vehicle must address those issues in an acceptable way while providing service personnel with the capabilities needed to service the vehicle.